PPARD and actinic keratosis: The basement membrane between the basal keratinocyte layer and the adjacent stroma exhibited a clear lining of laminin 332 in Pparβ/δ−/− actinic keratosis with moderate atypia (grade II) whereas laminin 332 deposition was more diffuse and thicker in lesions of wild-type mice, reflecting perturbations of the basal layer.